How would they generate ROI on the investment? Google has no track record with social media, if anything they lack creativity more than Twitter does. There is also no argument for a supplementary role to their other product lines.

Twitter just has to be allowed to be Twitter and not some amalgamation that competes with Facebook in usage metrics when it's an entirely different experience. I know, whatever was on those slides promising the world to early investors are going to make for a hard pill to swallow, but Twitter is reasonably successful imo.